Pneumatic control system for a fuel burning apparatus or the like

ABSTRACT

This disclosure relates to a pneumatic control system for a clothes dryer wherein the flow of fuel to the main burner means is pneumatically controlled in such a manner that the ignition means for the main burner means must be first pneumatically actuated before the pneumatic control system will pneumatically open the fuel supply means to the main burner means, the control system including a pneumatically operated logic &#39;&#39;&#39;&#39;memory&#39;&#39;&#39;&#39; unit to assure that the ignition means is always pneumatically operated before the main burner means can be pneumatically operated to its on condition by a pneumatically operated &#39;&#39;&#39;&#39;nand&#39;&#39;&#39;&#39; unit each time there is a requirement to turn on the main burner means. The &#39;&#39;&#39;&#39;memory&#39;&#39;&#39;&#39; unit is prevented from transmitting atmosphere therethrough when being switched by its setting signal.

United States Patent 1191 Scott Aug. 28, 1973 PNEUMATIC CONTROL SYSTEMson A FUEL BURNING APPARATUS OR THE LIKE Primary Examiner-Henry T.Klinksiek D I s Assistant Examiner-Robert J. Miller [75] InventorAttorney-Candor, Candor & Tassone [73] Assignee: Robertshaw ControlsCompany,

Richmond, Va. 57] ABSTRACT [2211 Filed: 1971 This disclosure relates toa pneumatic control system [21] Appl. No.: 197,538 for a clothes dryerwherein the flow of fuel to the main v burner means is pneumaticallycontrolled in such a I Rchted Appmflon manner that the ignition meansfor the main burner DlVlSlOfl f SCI. NO. 5,709, Jan. 26, 1970, Pat. N0.means must be first pneumatically actuated before the 3,635,645.pneumatic control system will pneumatically open the fuel supply meansto the main burner means, the con- [52] US. Cl. 137/625. "0] systemincluding a pneumatically operated logic [51] Int. Cl F15!) /00, G05d16/00 unit to assure that the ignition means is ab [58] Field of Searchl37/625.66, 625.65, ways pneumatically operated before the main burner137/63022, 103 means can be pneumaticallyoperated to its on condition bya pneumatically operated nand unit each [56] Reference? Cited time thereis a requirement to turn on the main burner UNITED STATES PATENTS means.The memory unit is prevented from transmit- 3,s2s,4ss 9/1970 Kreuter etal l37/625.-65 x s atmosphere therethroush when being Switched y3,550,629 12/1970 Kreuter et a1 its setting signal. 7 3,550,847 12/1970Scott ..'137/625.66 3,563,507 11/1968 Nisley l37/625.66 x claims, 2DI'lWiIIZ Fisllm S u 87 5 131 W IIIA IZZA 123A I27A I H4A Q 1 |24A i '02IOB I g108' F I30 97 i we. 15 ./|Ol 1 BS- w ,I' I 15 1 1 5 I "'1 .p' "Iq "9 1 '5 l H5 23 III 4, /-8O .11 PNEUMATIC- CONTROL SYSTEM-FOR A. rum.BURNING APPARATUS on :rna LIKE This is a division, of application Ser.-N o. ',70r9, filed Jan. 26, 1970 nowU.S.-Pat.*No.13,635,645.

.This invention is related to the'pneumatic control systems and methodsset forth in thecopending patent applications, Ser. No. 7'l7,-'586,filed Apr. l, 1968 now U.,S.Pat. No. 3,522,661, and Ser. No. 732,784.,filed May 28, 1968 now U.S.-Pat.-No. 3,522,662, which are wherein theflow of fuel to the main burner .means thereof is controlled byanelectric ithennostat means that willnot permittheflow of fuel tothe mainburner means until after anelectrical ignition means has beenelectricallyactuated so as to assure that the flowof fuel to the main,burner means will-be properly ignited.

The first aforementioned patent application discloses and claimsapneumatic control-system for controlling the flowof fuel to a mainburner means of an apparatus or the like in such arnanner that theignition means for the main burner means must first be pneumatically.actuated each time before the control system will permit a flow of fuelto the main-burner means. The second aforementioned patent applicationrelates to a pneumatic control system for a fuel burning apparatus thathas fewer'control parts that the control system of the f rstaforementioned patent application as well as an improved arrangementthat is substantially fail-safe in the logic units thereof so that thesource of fuel will automatically be disconnected or-not beinterconnected to the main burner means upon any one or combination. ofa number of possible component failures. v l

v Accordingly, one of the features of this invention is to provide sucha pneumatic control, system which will perform the same functions asthe-control systems of the aforementioned patent applications whileproviding a more accurate and responsive system- In particular, theembodiment of this invention provides a pneumatically operated, logicmemory unit which isutilized in combination with a pneumaticallyoperated logie nan,d'u nit so that. the samemust each receive particularpneumatic signals from the control system before, the nand unit willpneum i lly turn on the main burnermeans, the pneumatically operatedlogic na nd. unit-only, causing the fuel" source to. be interconnected,to, the burner means if the, pneumatically operated ignition meansof'the control system. has been first pneumatically actuated! toignition; condition as will be apparent hereinafter. The memory unitprevents the flow of atmosphere therethrough during the switching of the"memory" unit by itscontrol, signal.

Accordingly, it is an. objectof this inventionrtov provide an. improved,pneumatic control. system for a fuelburning apparatus or the like, thesystem. of this inventionv havingjoneor more of'the novel. featuresfsetforth above or hereinafter shownor described.

Other objects, uses and. advantages. of this invention are apparentfroma, reading of; this description which proceedswithreference tothe-accompanying drawings" forming a part thereof and wherein;

FIG. 1,,is1 a schematic view illustrating the improved. control system.of this invention.

Q2 FIG..2 is an enlarged, fragmentary view of the pneumatically operatedlogic units of the control system of FIG. 1 with the logic units beingillustrated in cross section.

'While'the various features of this invention arehereinafter describedand illustrated as being particularlyadapted to pneumatically controlthe operation of a domestic clothes dryer or thelike, it isto beunderstood that thevarious features of this invention-can be utilizedsingly or in any combination'thereof toprovide control means forothertypes of apparatus as desired.

Therefore, this invention is notto be limited'to only the embodimentsillustrated in the drawings, because the drawings are merely utiliz'edtoillustrate one of the wide variety of uses of this invention.

Referring 'now to FIG. 1, the improved control system of this inventionis generally indicated by the refer ence numeral 10 and is utilized forcontrolling'the operation of a clothes dryer,v generally indicated bythe reference numeral '1 1, having a main burner means 12 adapted to beinterconnected to a fuel source manifold '13 by apair of pneumaticallyoperated valve means14 and 14. in a manner hereinafter described.

7 The apparatus 11 includes an electric motor 15 which rotatestheclothes-receiving drum (not shown) of the apparatus 11 during theentire cycle of operation of the-apparatus 11 in a conventional manner,the elec tric motor 15 being adapted to be interconnected' system 10 ofthis invention as long as the electric motor 15 is energized, the vacuumpump means 19 having its inlet 20 interconnected to 'a conduit means 21.

The power source lead L is interconnected to one side 22 of the electricmotor 15 by a'lead 23. The other power source lead Lis interconnected bya lead 24 to a conventional timer operated switch blade 25 that has itscontact 26. cooperable with a fixed contact 27 that is interconnected bya lead 28 to a dryer door operated switch blade 29. The dryer dooroperated switch blade 29 has a contact 30 cooperable with a contact 31that is interconnected by a lead 32 to the other side 33 of the electricmotor 15.

Therefore, it can be seen that in order for the electric motor 15 to beplaced across the power leads L and L? for the electric motor 15 to beenergized, not only must the dryer door be disposed in its closedposition to close and hold the switch blade 29 against the contact 31,but also the housewife or the like must manually set the cycle timermeans (not shown) of the control sysa tem 10 so. that the same is in anon condition to hold the switch blade 25 against the contact 27 for apreset time period after the lapse of which the timer cycle means willautomatically open the switch blade: 25 away from the contact 27 toterminate the operation of the control system 10 in a conventionalmanner.

The pneumatically operated valve means 14 and-LL14" for interconnectingthe fuel source conduit 13 to the main burner means 12' of the apparatus11 are identical inconstruction and operation and while one such'valvemeans could properly control the on-off condition of a valve seat 36that interconnects its fuel source inlet 37 to its fuel source outlet38, the valve seat 36 being opened and closed by a valve member 39 thatismoved between its opened and closed positions by a vacuum operatedactuator that is generally indicated by the reference numeral 40. Thevacuum operated actuator 40 comprises a cup-shaped housing member 41having its open end 42 closed by a flexible diaphragm 43 that isinterconnected to the valve member 39 by a tying means 44 in aconventional manner whereby the flexible diaphragm 43 cooperates withthe housing 41 to define a chamber 45 therebetween. A compression spring46 is disposed in the chamber 45 to tend to normally move the flexiblediaphragm 43 upwardly as illustrated in FIG. 1 to maintain the valvemember 39 in its closed position against the valve seat 36 to preventany flow of fuel to the main burner means 12. However, when the vacuumsource 19 is interconnected to the chamber 45 in a manner hereinafterdescribed to evacuate the chamber 45, the pressure differential actingacross the diaphragm 43 moves the diaphragm 43 downwardly in oppositionto the force of the compression spring 46 to move the valve member 39 toits open position so that the fuel source 13 will be interconnected tothe main burner means 12 as long as the pneumatically operated actuators40 and 40' are in their actuated condition.

The ignition means for the main burner means 12 comprises an ignitioncoil 47 having one side 48 thereof interconnected by a lead 49 to thelead 24 through a door operated switch 29', similar to door switch 29,so that the side 48 of the ignition coil 47 is always interconnected tothe power source lead L when the dryer door is closed. The other sideSO-of the ignition coil 47 is interconnected by a lead 51 to a switchblade 52 that has a contact 53 cooperable with a contact 54 that isinterconnected to the power source lead L by a lead 55.

A vacuum operated actuator 56 controls theswitch blade 52 and comprisesa cup-shapedhousing 57 having its open end 58 closed by a flexiblediaphragm 59 that is interconnected to the switch blade 52 by a suitabletying means 60,'the flexible diaphragm 59 cooperating with the housing57 to define a chamber 61 therebetween that receives a compressionspring 62 that normally tends to urge the flexible diaphragm 59 upwardlyto hold the switch blade 52 out of contact with the contact 54 andthereby maintain the ignition coil 47 in its de-energized condition.However, when the chamber 61 of the actuator 56 is interconnected to thevacuum source 19 in a manner hereinafter described, the resultingpressure differential acting across the diaphragm 59 moves the diaphragm59 downwardly in opposition to the force of the compression spring 62 toplace the switch blade 52 into contact with the contact 54 so as toplace the ignition coil 47 across the power source leads L' and L.

When the ignition coil 47 is placed across the power source leads I. andL by the vacuum operated actuator 56 in a manner hereinafter described,the ignition coil 47 subsequently heats up to a temperature that will besufficient for igniting fuel issuing from the main burner means 12 in aconventional igniting manner.

An ignition coil temperature sensing means 63 is provided for the system10 and comprises a bimetal member 64 that is interconnected to a valvemember 65 by a typing means 66, the valve member 65 being disposed in ahousing means 67 having a valve seat 68 fluidly interconnecting aconduit 69 to a conduit 70. When the bimetal member 64 senses atemperature of the ignition coil 47 below a temperature sufficient forigniting fuel issuing from the main burner means 12, the bimetal member64 is in such a condition that the same maintains the valve member 65away from the valve seat 68 and against a valve seat 68 that leads tothe atmosphere so as to fluidly interconnect the conduits 69 and 70together. However, when the ignition coil 47 reaches an ignitiontemperature, the bimetal member 64 warps in such a manner that the samemoves the valve member 65 against the valve seat 68 to terminate thefluid connection between the conduits 69 and 70 and opens the valve seat68' so that atmosphere is in terconnected to the conduit 70 for apurpose hereinafter described. lnaddition, when the main burner means 12is operating, the bimetal member 64 also senses the flames at the mainburner means 12 so that the bimetal member 64 will maintain the valvemember 65 in its closed position against the valve seat 68 as long asfuel is burning at the main burner means 12.

Another temperature sensing device 71 is provided for the control system10 and is adapted to sense the temperature effect of the main burnermeans 12. The temperature sensing means 71 comprises a bimetal member 72that is interconnected to a valve member 73 by a tying means 74, thevalve member 73 being disposed in a housing means 75 to open and close avalve seat 76 thereof that is adapted to fluidly interconnect theatmosphere with the interior of the housing 75 when the valve seat 76 isopen. However, when the valve seat 76 is closed, the housing 75, ineffect, interconnects the conduit 21 to the conduit 69 of the ignitiontemperature sensing means 63.

As long as the temperature effect of the burner means 12 of theapparatus 11 is below a predetermined temperature effect setting of thesensing means 71, the bimetal member 72 maintains the valve member 73against the valve seat 76 to, in effect, fluidly interconnect theconduits 21 and 69 together whereby if the electric motor 15 isenergized, the vacuum source 19 will be interconnected to the conduit69. However, when the temperature sensing means 71 senses a temperatureeffect of the burner means 12 above the set temperature effect settingof the thermostatic means 71, the bimetal member 72 warps in a manner tomove the valve member 73 away from the valve seat 76 and, thus, ineffect, disconnects the vacuum source 19 from the conduit 69 as theatmosphere is now interconnected to the conduit 69 through the openedvalve seat 76 for a purpose hereinafter described. Of course, it is tobe understood that the sensing device 71 could be manually adjustablefor temperature selection purposes by the housewife or the like or couldbe factory set for an optimum drying temperature for the apparatus 11.

The conduit 69 is interconnected by a conduit 77 to a port means 78 of apneumatically operated logic memory" unit 79 later to be described, theconduit 77 check valve 88, the conduit 70 having a restriction 7 means89 therein in advance of the conduit 86 The'check valve 88 comprises ahousing means 90 having a valve seat 9;] adapted to beopened andclosedby avalve member 92, the valve seat 91 being adapted to interconnect theconduit 86 at the side 87 thereof to the otherside 93 of the check valvev 88 that leads to a conduit 94. The 'valve member 92 normally seatsagainst the valve seat 91 to prevent fluid communication between theconduits 86 and 94 so that when the conduit 70 is interconnected to thevacuum source 19 by the valve means 63 and 71 being disposed in thepositions of FIG. 1, the vacuum source 19 opens the valve member 92 awayfrom the valve seat 91 so as to beinterconnected to the conduit 94.

The conduit 94 is'fli idly nterc n ected to a ondu 95 that has one end96 thereof interconnetd to a port means of the logic memory unit 79while the other end 98 of the conduit 95 is interconnected to anotherport means 99 of the logic memory unit 79.

The conduit 95 is fluidly interconnected to a conduit 101 that leads toa portmeans 102 of the logic .-nand" unit 2 he logic Wa d" uni -havingan th p means thereof fluidly interconnected to a conduit means 104 thatis fluidly interconnected to branch conduit m ans 105 and 10. t a are epe ti ly fluidly interconnected tothe chambers 45 and 45' of thevac; uumactuators 40 jand 40'. The branch conduits 105 and-105' respectivelyhave restrictions 107 and 107! therein. a

. 'The conduit 104 intermediate the. actuators 40 and 40 a d he nan-dunit 2 s nterconnected e mosphere by a controlled bleed means 100 for apurpose hereinafter described. However, the controlled bleed meansinterconnects, thev conduit 104 to the atmosphere at a controlled ratethat is less than the effective rate of fluid interconnectionprovided bythe restriction 83 in the conduit 77 as willbe apparent hereinafter.

The conduit 70 leadingfromthe ignition temperature sensing means 63 isfluidly interconnected to a conduit 06. tha s. flui y n erq nccted o hehamb r 61 0f theactuator 56, t

A remaining port means 108 of thelogic nand"u nit 8 2 isinterconnectedto the atmospherethrough a filter 10,8" anda port means1090f the logic memory" unit 79- is interconnected to the atmosphere.

Theremaining port means 110- of the "memory" unit 79 isinterconnectedbyaconduit [f to the conduit 70 intermediate therestriction 89and the sensor 63for P rpo hereinafter described an tothetmosph re through. a restriction 100,, the conduit 110' having a one-waycheclg valve 88 similar to the check. valve 88 whereby like parts, areindicated by like reference numerals followed by, aprime mark.

As previously stated, the control system 10 is so constructed andarranged that the ignition coil-47'for the burnermeans 12 must be firstenergized to a tempera? ture thereof that willbe sufficient for ignitingfuel issuing from the burner means 12 each time before the actuators 40and 40 will be actuated tosimultaneously move the valve members 39 and39 from their closed positions to their open positions to cause fuel toissue from the main burner means 12.

Thus, since both temperature sensing devices'63 and 71 are normallydisposed in the positions illustrated in FIG. 1 when the control systeml0is initially turned on by the housewife or the like setting the timercycle means in its on" position to close the switch blade 25 against thecontact 27, the thus energized velectric motor 15 will operate'thevacuum pump 19 and since the temperature effect of the apparatus 11 isbelow the temperature effect setting of the thermostatic device 71, thevacuum pump 19 is adapted to evacuate the conduit 69 through the closedhousing 75 as well as to evacuate the conduit means 70 and 77 leadingrespectively to the logic memory unit 79 and logic nand unit 82.

The logic nand unit 82 will now receive a pneumatic signal at the portmeans 102 thereof from the memory? unit 79 as well as a pneumatic signalat the port means 85 thereof as long as thevalve member 65 of theignition temperature sensing means 63 is in its open position from thevalve seat .68 and is closed against the valve seat 68' whereby the nandunit will be in a de-activated condition to prevent the vacuum source 19from being interconnected to the conduit 104 so that the valve means 14and 14' remain in their closed positions to prevent fuel from reachingthe main burner means 12. However, aftervthe ignition coil 47 reachesits ignition condition, the valve means 65 closes against the valveseat68 and opens, the valve seat 68' so as to terminate the pneumatic signalto the port means 85 of the nand unit 82 whereby the "nand unit 82 willnow be activated to a condition thereof to interconnect the vacuumsource 19 to the conduit 104 so that the actuators 40 and 40 will beevacuated to open the valve members 39 and 39 so that fuel can issuefrom the burner means 12 and be ignited by the ignition means 47. 7Accordingly, the logic units 79 and 82 always require that the valvemember 65 must first be in its open position away from the valve seat 68and then be moved to a closed position against the valve seat 68 aftereach closing of the main valve means 14 and 14' before the main valvemeans 14 and 14 can be again opened, the valve member 65 only closingagainst the valve seat 68 after an open condition thereof by theignition coil 47 being energized to a temperature suitable for ignitingfuel that is to subsequently issue from the mainburner means 12.

The details of the logic units 79 and 82 for accomplishing the abovefunction will now be described in detail'whereby reference is now madeto FIG. 2. As illustrated in'FlG. 2, the logic units 79 and 82 aresubstantially identical in construction whereby only the particulardetails of the logic memory unit 79 will now be described and like partsof the logic nand" unit 82 will be indicated by the same referencenumer-- als followed by the reference letter A". In this manner, it willbe appreciated that the logic units of this invention can be made fromthe same parts in asimple and effective manner while producingdifferentlogic tively small when considering the costs of prior knownelectrical and pneumatic control systems.

As illustrated in FIG. 2, the logic memory unit 79 comprises two housingparts 111 and 112 suitably secured together to hold two annular members113 and 114 between the opposed and respective inner end wall means 115and 116 thereof. A flexible, one-piece diaphragm member 117 is disposedin the housing means 111 and 112 and has an intermediate or largecentral outwardly directed diaphragm portion 118 provided with an outerperipheral portion 119 that is secured and sealed between the annularmembers 113 and 1 14. An outboard smaller spaced diaphragm portion 120of the diaphragm member 117 has its outer periphery 121 secured andsealed between the housing member 111 and the annular member 113 todefine a chamber 122 between the diaphragm portion 120 and the end wallmeans 115 of the housing member 111 while cooperating with the largercentral diaphragm portion 118 to define a chamber 123 between thediaphragm portions 1 18 and 120. An opposed smaller outboard spaceddiaphragm portion 124 of the diaphragm member 1 17 has its outerperiphery 125 secured and sealed between the annular member 114 and thehousing member 112 to define a chamber 126 between the diaphragm portion124 and the end wall means 1 16 of the housing member 112 whilecooperating with the central diaphragm portion 118 to define a chamber127 between the diaphragm portions 118 and 124.

The diaphragm member 117 has a bore 128 interrupting the end 129 thereofso as to receive a compression spring 130 that has one end bearingagainst the end wall means 116 of the housing member 1 12 and the otherend thereof bearing against the diaphragm member 117 to normally urgethe diaphragm portion 120 against a frustoconical valve seat .131 thatprojects-inwardly from the end wall means 115 of the housing member 111into the chamber 122. The valve seat means 131 of the logic memory unit79 is interconnected to the port means 78 thereof that leads to theconduit 77 whereas the valve seat means 131A of the nand" unit 82 isinterconnected to the port means 81 that leads to the conduit 80.

The diaphragm member 117 has a passage means 132 passing through thediaphragm portion 120 in offset relation to the valve seat 131 so as toalways fluidly interconnect the chambers 122 and 126 together, thepassage 132 also being in offset relation to a frustoconical valve seat133 that projects inwardly from the end wall means 115 of the housingmember 112 and is received in the bore' 128 of the diaphragm member 117to be opened and closed by the end wall 134 of the diaphragm member 117that defines the closed end of the bore 128 and forms part of theeffective surface of the diaphragm portion 124 that defines the chamber126. The valve seat 133 of the logic memory" unit 79 is interconnectedto the port 110 which leads to the conduit 110! and the valve seat 133Aof the logic nand" unit 82 is interconnected to the port means 108 thatleads to the atmosphere.

The port means 78 and 99 of the housing member 111 and the port means110 of the housing member 112 can comprise outwardly extending tubularnipples that can be effectively telescoped into flexible conduit meansto fluidly interconnect the same to such conduit FIG. 2, the nipple portmeans 99 and 78 of the logic memory unit 79 are fluidly interconnectedrespectively to the conduits 98 and whereas the nipple port means 81 and103 of the logic nand unit 82 are respectively interconnected to theconduits and 104.

The annular member 114 carries the port means 97 in the form of a nippleextension projecting out of an opening means 135 in the housing member 112 and the port means 109 comprises a nipple extension of the annularmember 113 projecting out of an opening means 136 of the housing member1 1 1. The nipple port means 97 of the logic memory unit 79 isinterconnected to the end-96 of the conduit member 95 and the nippleport means 109 is interconnected to the atmosphere whereas thecorresponding nipple port means 102 and 85 of the logic nand unit 82 arerespectively interconnected to the conduits 101 and 70.

Accordingly, it can be seen that the chamber 122 of the logic memory"unit 79 is always interconnected to the port means 99 and, thus, to theend 98 of the conduit whereas the port means 78 and, thus, the conduit77 is adapted to be interconnected to the chamber 122 when the diaphragmmember 117 opens the valve seat 131. The atmosphere port means 109 isalways interconnected to the chamber 123. The chamber 127 is alwaysinterconnected by the port means 97 to the end 96 of the conduit means95. As previously stated, the chamber 126 is always interconnected tothe chamber 122 by the passage means 132 and is adapted to beinterconnected to the atmosphere or effectively blocked from theatmosphere at the port means 110 except for the controlled rate providedby the bleed restriction 100' when the diaphragm member 117 opens thevalve seat 133 depending on whether the valve 88 is open or closed aswill be apparent hereinafter.

In regard to the logic nand" unit 82, the chamber 122A thereof is alwaysinterconnected by the port means 103 to the conduit 104 and is adaptedto be in-- terconnected to the port means 81 and, thus, to the conduit80 when the diaphragm member 117A opens the valve seat 131A, the chamber122A always being interconnected to the chamber 126A by the passagemeans 132A in the diaphragm member 117A. The chamber 123A is alwaysinterconnected by the port means 85 to the conduit 70. The chamber 127Ais always interconnected by the port means 102 to the conduit 101. Thechamber 126A, while always being interconnected to the chamber-122A bythe passage means 132A in the diaphragm member 1 17A, is adapted to beinterconnected to the atmosphere at the port 108 when the diaphragmmember 117A opens the valve seat 133A.

The operation of the control system 10 of this invention will now bedescribed.

Assuming that the dryer door is in its closed position to hold theswitch blades 29 and 29' in their closed positions, the housewife or thelike sets the timer selector means for operating the dryer 1 1 for apredetermined length of time whereby the timer mechanism closes andholds the switch blade 25 against the contact 27 and will maintain theswitch blade 25 against the contact 27 during the entire cycle ofoperation of the dryer 11 so that at the conclusion of such time period,the timer means will automatically open the blade 25 away from thecontact 27 to terminate the operation of the apparatus 11.

With the switch blade 25 now movedto its closed position against thecontact 27, it can be seen that the electric motor 15 is placed, acrossthe power source the clothes in an atmosphere to be heated by the burnermeans 12 for drying of the laundry, or the like. As the output shaft 17of the motor, 15 is continuously, rotating, the same throughtheeccentricicam l6 reciprocates suitable pumping mechanism of thevacuum pumpg19 to continuously provide a vacuum source for the controlsystem 10.

At the initial operation ofethecontrol system 10, not only is theignition coil 47 not atan ignition temperature, but also the temperatureeffect of theapparatus 11 is below-thetemperature effect setting of thethermostatic means 71 whereby both valve members 65 and 73 are inthepositionas illustrated in FIG. 1 sovthat the vacuum source 19is notonly-interconnected to the vacuum operated actuator56'to evacuate thechamber 61 thereof and close the switch blade 52 against the contact 5 4to place the ignition coil 47 across the power source leads I and L but,also'the vacuum source 19 is interconnected by the conduits 77 and 80to the valve seats 13! and 131A of the memory unit 79 and nand unit 82,which valve seats 13] and 131A are normally closed by the diaphragmmembers 117 and 117A due to the force .of the respective compressionsprings 130 and 130A, and by the conduit means 70 to the chambers 127and 122 of the memory unit 79 and the chamber 123A of the nand unit 82.The vacuum in the conduits 70 and 110' causes the check valve 88 toclose so that the open valve seat 133 of the memory unit 79 iseffectively blocked from the atmosphere as the bleed 100' does noteffect evacuation of chamber 126.

In particular, since the conduit 70 is interconnected to the inlet 20 ofthe vacuum pump 19 by the positioned valve members 65 and 73, the vacuumpump 19 can evacuate the chamber 123A of the nand unit 82 to maintainthe diaphragm member 117A thereof in its de-activated and seatingposition against the valve seat 131A so that the vacuum source in theconduit '80 leading to the valve seat 131A cannot reach the actuators 40and 40' to open the valve means 14 and 14.

Also, since the conduit 86 is now being evacuated, the checkvalve 88opens whereas the check valve 88', closes so that the conduit 95 can beevacuated whereby the'end 96 thereof evacuates the chamber 127 of thememory unit 79 so that the resulting pressure differential acting acrossthe large central diaphragm portion 118 causes the diaphragm member 117to move upwardly in FIG. 2 in opposition to the force of the compressionspring 130 to its activated position to open the valve seat 131.

However, before, the evacuation of the chamber 127 of the memory unit79. can effect the switching of the diaphragmmember 117 upwardly in FIG.2, the vacuum source 19 now, being interconnected to the chamher 126 bythe way of conduit 95,,chamber 122 and diaphragm passagel32 to chamber126, assists in the complete evacuation of the chamber 122 so that whenthe diaphragm member l17 does switch to its up position in FIG. 2, noatmospheric pressure is permitted to pass out into the conduit 95 and,thus, slow down or prevent the setting of the fmemory unit 79 in its onposition.

With the valve seat 131 now being opened by the activated memory unit79, the vacuum source 19 is interconnected by the conduit 77 through therestriction means 83 to the chamber 1220f the memory unit 79 so that theconduit 101 effectively leading from the chamber 122 of the memory unit79 is evacuated to evacuate the chamber 127A of. the nand unit 82.

With the chamber 127A of the nand" unit 82 now being evacuated, it canbe seen that as long as the valve member 65 of the ignition temperaturesensing means 63 is in its seated position against the valve seat 68,the opposing chamber 123A of the nand unit 82 is also evacuated so thatan equal vacuum condition exists across the central diaphragm portion118A of the diaphragm member 117A of the nand" unit '82 so that thecompression spring 130A maintains the diaphragm member 117A in its up orde-activated position in FIG. 2 to maintain the valve seat 131A'thereofclosed and the chamber 122A thereof that leads to the chambers 45 and 45of the actuators 40 and 40 of the valve means 14 and 14 interconnectedto the atmosphere through the passage means 132A of the diaphragm member117A and the open valve seat 133A whereby the valve members '14 and 14'cannot be opened to interconnect the fuel source 13 to the main burnermeans 12 as long as a vacuum signal is directed to the chamber 123A bythe ignition sensing means 63.

However, when the energized ignition coil 47 subsequently heats up toignition condition, the sensing member 64 warps downwardly in FIG. 1 toopen the valve seat 68' and close the valve member 65 against the valveseat 68 and thereby disconnect the vacuum source 19 from the conduit 70which begins to return to atmospheric condition by the opened valve seat68' so that not only is the chamber 61 of the actuator 56 returned toatmospheric condition to open the switch blade 52 away from the contact54 and deenergize the ignition coil 47, but also the chamber 123A of thenand unit 82 returns to atmospheric condition whereby the resultingpressure differential acting across the diaphragm portion 1518A of thediaphragm member 117A of the nand unit 82 causes the diaphragm member117A to move downwardly in FIG 2 in opposition to the force of thecompression spring A to its activated position to not only open thevalve seat 131A to the chamber 122A, but also to close the valve seat133A from the chamber, 126A.

In this manner, since the valve member 73 of the temperature effectsensing means 71 in its open condition, the vacuum source 19, in effect,is interconnected to the chambers 45 and 45 of the actuators 40 and 40'to move the valve members 39 and 39' to their open position so that thefuel source 13 is now interconnected to the main burner means 12 and isignited by the ignition coil 47. x

As previously stated, when the valve member 65 0f the ignitiontemperature sensing means 63 is moved to its closed position against thevalve seat 68 to permit the now opened valve seat 68 to return theconduit to atmospheric condition to terminate the vacuum sig nal to thechamber 123A of the nand unit 82 so as to activate the same, the checkvalve 88 closes so that such return of air into the conduit 70 cannotreach the conduit 94 whereby the diaphragm member 117 of the memory unit79 remains in its actuated condition wherein the valve seat 131 is inits open condition and the valve seat 133 is in its closed condition sothat a continuous vacuum signal is directed from the chamber 122 to thechamber 127A of the nand unit to maintain the nand" unit in itsactivated position for maintaining the valve means 14 and 14. in theiropen condition, the restriction 83 providing a greater flow than thecontrolled bleed means 100 in the conduit 104 so that the valve means 14and 14' remain open. A holding circuit is provided for the memory unitfrom the vacuum source 19 to the chamber 122 of the memory unit 79 andby means of the conduit 95 to the chamber 127 to, maintain the diaphragmmember 117 in its up or activated position. Also, the return of air intothe conduit 70 causes the check valve 88 to open whereby atmosphere isat the closed valve seat 133 of unit 79.

Thus, since flames now exist at the main burner means 12, thetemperature sensing means 63 will maintain the valve member 65 closedagainst the valve seat 68 so that the burner means 12 will continue tooperate unless the temperature effect being produced by the burner means12 exceeds the predetermined temperature effect setting of thethermostat means 71.

If the temperature effect of the burner means 12 exceeds the setting ofthe thermostat 71, the temperature sensing member 72 will move the valvemember 73 away from the valve seat 76 to effectively disconnect theconduit 77 from the vacuum source 19 whereby the air will return notonly to the chamber 127 of the memory unit 79 through the opened valveseat 131 to de-activate the same, but also permit air to return to thechamber 127A of the nand unit 82 whereby the compression spring 130A ofthe nand unit 82 will move the diaphragm member 117A upwardly to closethe valve seat 131A and open the valve seat 133A so that the chambers 45and 45' and the actuators 30 and 30' will be interconnected to theatmosphere by the passage means 132A in the diaphram member 117A leadingto the chamber 126A that is interconnected to the open valve seat 123Aas by leads to the atmosphere at the port 108 as well aby the bleedmeans 100 in the conduit 104. Similarly, the diaphragm member 117 of thememory unit 79 moves downwardly in H6. 2 under the force of thecompression spring 130 because the chamber 127 returns to atmosphericcondition so that the valve seat 131 is now closed and the valve seat133 is opened to return the chamber 126 to atmospheric condition.

Since flames do not now exist at the main burner means 12, the ignitiontemperature sensing means 63 now causes the valve member 65 to move awayfrom the valve seat 68 and against the valve seat 68' so that when thevalve member 73 of the thermostat 71 is again moved to its closedcondition against the valve seat 76 by the temperature effect in thedryer ll falling below the set temperature effect of the thermostat 71,the main burner means 12 will be operated in the manner previouslydescribed wherein the igniter means 47 will again be first energized toignition condition before the valve members 14 and 14' can be opened.

However, if during the normal operation of the control system 10,wherein the main burner means 12 has been interconnected to the fuelsource 13 in the manner previously described so as to be continuouslybuming, the housewife or the like should open the dryer door temporarilyto cause the switch blades 29 and 29' to open so as to disconnect theelectric motor 15 from the power source leads L and L whereby the vacuumsource 19 ceases to function so that the control system bleeds toatmospheric condition by the controlled bleed 100, and the housewifesubsequently closes the dryer door to again activate the motor 15 beforethe ignition temperature sensing means 63 has moved the valve member 65away from the valve seat 68, the nand unit 82 cannot cause reopening ofthe valve means 14 and 14 because the memory unit 79 has not been resetto its activated position so as to interconnect the conduit 77 to thechamber 122 thereof and, thus, to the chamber 127A of the nand unit 82as it requires an opening of the valve member 65 away from the valveseat 68 of the ignition temperature sensing means 63 to activate thememory unit 79 and the nand" unit 82 requires a subsequent closing ofthe valve member 65 against the valve seat 68 to terminate the vacuumsignal to the chamber 123A thereof before the nand unit 82 can beactivated to cause opening of the valve means 14 and 14'.

Thus, it can be seen that the control system 10 of this inventionutilizes only two logic units each formed of identical structure butperforming different logic functions in a manner to control the mainburner means 12 so that the system requires that the ignition means 47be always pneumatically operated to ignition condition before the mainburner means 12 can be pneumatically operated to its on condition eachtime there is a requirement to turn on the main burner means.

Further, it can be seen that the logic unit 79 of this invention is soconstructed and arranged that during the time of switching the memoryunit 79, no atmospheric signal is seen by the unit 79 to slow down orprevent its switching operation.

Further, any clogging of the restrictions 89 and 83 by dirt or the likeduring the operation of the system 10 will not cause an adversesituation as the bleed means will cause the valve means 14 and 14 toclose and thereby terminate the operation of the burner 12.

Thus, it can be seen that this invention provides an improved pneumaticcontrol system for a fuel burning apparatus or the like.

What is claimed is:

l. A pneumatically operated control system comprising a pneumaticsource, a pneumatically operated unit having a housing means carrying aplurality of spaced diaphragm means that move in unison relative to saidhousing means and cooperate therewith to define at least first,- secondand third chambers in stacked relation, said housing'means having firstand second valve seats leading respectively to said first chamber and tosaid third chamber and being adapted to be opened and closed by saiddiaphragm means, first means for interconnecting said source to saidsecond chamber to move said diaphragm means to close said first valveseat and open said second valve seat and for interconnecting theatmosphere to said second chamber to cause said diaphragm means to moveto close said second valve seat and open said first valve seat, secondmeans for interconnecting said source to said second valve seat, saiddiaphragm means having passage means therethrough always interconnectingsaid first and third chambers together, said first means alsointerconnecting the atmosphere to said first valve seat at substantiallythe same time it interconnects the atmosphere to said second chamber andhaving disconnecting means to disconnect the atmosphere from said firstvalve seat when said first means is interconnecting said source to saidsecond chamber whereby said first chamber is disconnected from theatmosphere during the time it takes said second chamber to switch saiddiaphragm means from closing said second valve seat to opening saidsecond valve seat.

2. A pneumatically operated control system as set forth in claim 1wherein spring means is carried by said housing means and is operativelyassociated with said diaphragm means to tend to normally maintain saiddiaphragm means in a position thereof that closes said second valveseat.

3. A pneumatically operated control system as set forth in claim 1wherein said housing means has a passage interconnecting said thirdchamber with the exterior of said housing means regardless of theposition of said diaphragm means.

4. A pneumatically operated control system as set forth in claim 1wherein said first means include a passage defining means between saidsource and said first and second chambers, said passage defining meanshaving a restriction means therein.

5. A pneumatically operated control system as set forth in claim 4wherein said passage defining means has a part thereof bypassing saidrestriction and leading to said first valve seat.

6. A pneumatically operated control system as set forth in claim 5wherein said part of said passage defining means has a one-way checkvalve therein that defines said disconnecting means of said first means.

7. A pneumatically operated control system as set forth in claim 4wherein a one-way check valve means is disposed in said passage definingmeans between said restriction means and said second chamber.

8. A pneumatically operated control system as set forth in claim 7wherein said housing means has a passage interconnecting said thirdchamber with the exterior of said housing means, said passage definingmeans being interconnected to said passage. 7

9. A pneumatically operated control system as set forth in claim 1wherein said source is a vacuum source.

10. A pneumatically operated control system comprising a pneumaticsource, a pneumatically operated unit having a housing means carrying amovable means that cooperates therewith to define at least first, secondand third chambers in stacked relation, said housing means having firstand second valve seats leading respectively to said first chamber and tosaid third chamber and being adapted to be opened and closed by saidmovable means, first means for interconnecting said source to saidsecond chamber to move said movable means to close said first valve seatand open said second valve seat and for interconnecting the atmosphereto said second chamber to cause said movable means to move to close saidsecond valve seat and open said first valve seat, second means forinterconnecting said source to said second valve seat, said movablemeans having passage means therethrough always interconnecting saidfirst and third chambers together, said first means also interconnectingthe atmosphere to said first valve seat at substantially the same timeit interconnects the atmosphere to said second chamber and havingdisconnecting means to disconnect the atmosphere from said first valveseat when said first means is interconnecting said source to said secondchamber whereby said first chamber is disconnected from the atmosphereduring the time it takes said second chamber to switch said movablemeans from closing said second valve seat to opening said second valveseat.

1. A pneumatically operated control system comprising a pneumaticsource, a pneumatically operated unit having a housing means carrying aplurality of spaced diaphragm means that move in unison relative to saidhousing means and cooperate therewith to define at least first, secondand third chambers in stacked relation, said housing means having firstand second valve seats leading respectively to said first chamber and tosaid third chamber and being adapted to be opened and closed by saiddiaphragm means, first means for interconnecting said source to saidsecond chamber to move said diaphragm means to close said first valveseat and open said second valve seat and for interconnecting theatmosphere to said second chamber to cause said diaphragm means to moveto close said second valve seat and open said first valve seat, secondmeans for interconnecting said source to said second valve seat, saiddiaphragm means having passage means therethrough always interconnectingsaid first and third chambers together, said first means alsointerconnecting the atmosphere to said first valve seat at substantiallythe same time it interconnects the atmosphere to said second chamber andhaving disconnecting means to disconnect the atmosphere from said firstvalve seat when said first means is interconnecting said source to saidsecond chamber whereby said first chamber is disconnected from theatmosphere during the time it takes said second chamber to switch saiddiaphragm means from closing said second valve seat tO opening saidsecond valve seat.
 2. A pneumatically operated control system as setforth in claim 1 wherein spring means is carried by said housing meansand is operatively associated with said diaphragm means to tend tonormally maintain said diaphragm means in a position thereof that closessaid second valve seat.
 3. A pneumatically operated control system asset forth in claim 1 wherein said housing means has a passageinterconnecting said third chamber with the exterior of said housingmeans regardless of the position of said diaphragm means.
 4. Apneumatically operated control system as set forth in claim 1 whereinsaid first means include a passage defining means between said sourceand said first and second chambers, said passage defining means having arestriction means therein.
 5. A pneumatically operated control system asset forth in claim 4 wherein said passage defining means has a partthereof bypassing said restriction and leading to said first valve seat.6. A pneumatically operated control system as set forth in claim 5wherein said part of said passage defining means has a one-way checkvalve therein that defines said disconnecting means of said first means.7. A pneumatically operated control system as set forth in claim 4wherein a one-way check valve means is disposed in said passage definingmeans between said restriction means and said second chamber.
 8. Apneumatically operated control system as set forth in claim 7 whereinsaid housing means has a passage interconnecting said third chamber withthe exterior of said housing means, said passage defining means beinginterconnected to said passage.
 9. A pneumatically operated controlsystem as set forth in claim 1 wherein said source is a vacuum source.10. A pneumatically operated control system comprising a pneumaticsource, a pneumatically operated unit having a housing means carrying amovable means that cooperates therewith to define at least first, secondand third chambers in stacked relation, said housing means having firstand second valve seats leading respectively to said first chamber and tosaid third chamber and being adapted to be opened and closed by saidmovable means, first means for interconnecting said source to saidsecond chamber to move said movable means to close said first valve seatand open said second valve seat and for interconnecting the atmosphereto said second chamber to cause said movable means to move to close saidsecond valve seat and open said first valve seat, second means forinterconnecting said source to said second valve seat, said movablemeans having passage means therethrough always interconnecting saidfirst and third chambers together, said first means also interconnectingthe atmosphere to said first valve seat at substantially the same timeit interconnects the atmosphere to said second chamber and havingdisconnecting means to disconnect the atmosphere from said first valveseat when said first means is interconnecting said source to said secondchamber whereby said first chamber is disconnected from the atmosphereduring the time it takes said second chamber to switch said movablemeans from closing said second valve seat to opening said second valveseat.